1. Field of the Invention
The present invention relates to an actuator device for transmitting horizontal oscillatory movements to tube bars in knitting machines, said tube bars being supported, at the respective opposite ends, by at least two lifting plates slidably engaging them in a horizontal direction, said device comprising: a supporting framework rigidly connected to a base of said knitting machine; a plurality of movement rods each exhibiting one end operatively connected to one end of a corresponding tube bar; drive means acting on a second end of each movement rod opposite to said first end, for transmitting a horizontal oscillatory movement of variable amplitude to the corresponding tube bar, said horizontal oscillatory movement being combined with a vertical oscillatory movement imparted to the tube bars through said lifting plates, in order to give a plurality of threading tubes engaged to the tube bars a reciprocating motion according to a curved path extending astride of respective needles disposed consecutively in side by side relation, so as to cause the interlacing of the weft yarns with the warp yarns guided to the needles.
2. Prior Art
It is known that in knitting machines in general, and more particularly in crochet gallon looms the production of a manufactured article takes place through interlacing of weft yarns with warp yarns carried out at a plurality of needles disposed parallelly in side by side relation and spaced apart a given distance from each other on a front bar, and simultaneously operated in rectilinear reciprocating motion in a longitudinal direction. The warp yarns are engaged to respective eye-pointed needles located in front of the needles and driven in reciprocating motion according to a curved path astride of one or more of the needles themselves.
The weft yarns, in turn, are individually guided in respective threading tubes disposed mutually in side by side relation and distributed along one or more tube bars that are driven in reciprocating motion in such a manner that each threading tube travels along a curved path extending astride of one or more needles.
The above movement is achieved through the combination of a vertical reciprocating motion with a horizontal reciprocating motion.
The vertical reciprocating motion takes place by means of a pair of kinematic mechanisms consisting of a connecting rod-crank assembly driven by the main drive shaft of the machine and acting upon two support plates slidably guided in a vertical direction at the upper part of the base. Each of these plates is slidably passed through by the individual tube bars, at one of the ends thereof. Therefore all tube bars are simultaneously concerned with vertical movements, which movements perform a constant stroke.
On the contrary, as regards the horizontal movement, the individual tube bars are driven independently of one another, and the amplitude of the strokes thereof is varying each time, depending upon the number of needles that are to be each time stepped over by the threading tubes in order to achieve the desired pattern on the manufactured article being worked. To this end, the individual tube bars are connected, via movement rods engaging them at one of their ends, to corresponding drive members oscillatably linked to a fixed framework and designed to be activated by the so-called "glider chains".
Each glider chain is comprised of a plurality of cam elements, mutually linked one after the other so as to form a true chain extending in a closed loop. The individual chains are engaged on respective drive wheels disposed mutually in side by side relation close to said drive members and simultaneously driven in rotation such that the individual cam elements, against the action of return springs acting on the tube bars, give rise to reciprocating oscillations of the corresponding drive members of a variable amplitude depending on the geometric conformation of the cam elements. Corresponding to the oscillations of the individual drive members are horizontal oscillations of the respective tube bars.
It is to be pointed out in fact that each group of chains is suited for working one type only of manufactured article. It results therefrom that it is generally necessary to replace all glider chains present in the knitting machine each time the type of product being worked needs to be changed.
In addition to this requirement that by itself involves important labor times, generally there is also the problem that difficult operations are to be accomplished manually for assembling the individual cam elements so as to form the glider chains to be used for the new working. These assembling operations are very long in that, above all in case of rather complicated manufactured articles, each chain may need to be formed even with different hundreds of cam elements that must be selected one by one and linked together following a precise order depending upon the pattern to be formed on the manufactured article.
Furthermore, chains dismantled from the knitting machine must be generally taken to pieces in order to make the individual cam elements available for making new chains.
Therefore an important problem is also represented by the high costs for setting up a knitting machine, above all when small samples of the manufactured articles are needed.
Also of great importance are costs for purchasing the very great amount of cam elements necessary to make said chains. Further expenses arise from the necessity of having true stocks of said cam elements at one's disposal. Actually the cam elements stocked in a warehouse need to be classified based on their geometric configuration and stored in an orderly manner for the purpose of making them readily available.
Glider chains also exhibit limitations as regards their technical features. In particular, difficulties are encountered when the tube bars must carry out horizontal oscillations of relatively wide amplitude, so that the threading tubes can move astride of a plurality of needles. In fact the amplitude of stroke imparted to each tube bar depends on the lifting detectable in the cam element producing it. On the other hand, the use of cam elements having a lifting greater than given values would involve overstresses on the structures and driving mechanisms of the knitting machine, also resulting from the necessity of overloading the return springs in order to ensure constant contact of the drive members with the cam elements, above all at high operating speeds.